Referring to FIG. 3, it is generally known that robots 40 are used for industrial painting purposes, for example for painting motor-vehicle bodies. Robots 40 such as these have an atomiser apparatus 42, for example a high-speed rotating atomiser or an air atomiser. The workpieces 50 to be painted are normally located on a goods mount, which can be moved with the aid of a feed device 52, for example a floor conveyor or a hanging conveyor. This allows the workpieces 50 to be fed into and out of a painting cabin.
Depending on the given constraints, it is both planned practice for the workpieces 50 to be moved continuously by the feed device 52 during the painting process and for them not to be moved during the painting process.
A processing program 44 presets both the nominal movement of the atomiser device around the workpiece 50 to be painted, with this nominal movement being carried out by the robot 40, and the nominal atomiser parameters, by means of which the atomiser device 42 is operated. In this case, the atomiser device 42 is moved relative to the workpiece 50.
In an exceptional situation, for example in the event of an emergency stop, the processing program is interrupted immediately, that is to say the movement of the atomiser device is stopped and the atomiser apparatus is switched off, as a result of which the painting process is interrupted. Furthermore, the feed device is also stopped. After the interruption, the robot and the atomiser apparatus as well as the workpiece to be coated are in an undefined position with respect to one another, as a result of the mass inertia, because of the different and/or undefined braking response.
There are various procedures for restarting the coating process at or in the vicinity of the interruption point, in such a way that, as far as possible, the interruption does not result in any deterioration to the coating result on the workpiece to be coated.
One possible procedure is known from European Patent EP 0 285 075, in which the resumption of the movement of the atomiser apparatus takes place according to the prior art described therein, with the nominal velocity being suddenly preset. Because of the mass inertia of the coating apparatus, the actual velocity of the atomiser apparatus during the acceleration process is generally less than the nominal preset velocity. The resumption of the coating process, started at the same time, by use of the nominal atomiser parameters leads to the workpiece to be coated being overcoated during the acceleration process.
Furthermore, the resumption of the use of the nominal atomiser parameters in an initial phase is also accompanied by an unstable spraying process, which likewise has a disadvantageous influence on the coating quality achieved at the interruption point.